A variety of methods and devices for coating fibers with resin are known in the art. For example, U.S. Pat. No. 4,728,387 discloses an apparatus for coating a bundle of glass fibers which comprises at least one convex surface for separating the individual fibers of the bundles, and at least one nonconvex surface, along which the fiber bundle is passed under tension. The fibers are coated by injecting the resin through an orifice which opens upon the nonconvex surface.
The patented device has several drawbacks, however. In particular, the individual fibers of the bundle are not always properly separated from one another. That is, while sometimes the fibers are grouped at the vertex of the convex surface, at other times they form two or more separate bundles on either side of the vertex. This results in the formation of an irregular coating of resin on the fibers of the bundle. The present invention overcomes these drawbacks in the manner described below.